Pimelodella longipinnis (Borodin, 1927)

Slobodian, Veronica, Abreu-Santos, Bruno & Pastana, Murilo Nogueira de Lima, 2021, The rediscovery of Pimelodella longipinnis (Borodin, 1927), an enigmatic Atlantic Rainforest catfish species from Southeastern Brazil (Siluriformes: Heptapteridae), Papéis Avulsos de Zoologia 61, pp. 1-13 : 3-6

Pimelodella longipinnis (Borodin, 1927) Figs. 1-4 ; Table 1

Synonymy

Rhamdella longipinnis Borodin, 1927a: 6-7 (original description; “Prov. St. Paulo,?, Brazil ”; holotype: AMNH 8642). – Gosline, 1945: 35 (checklist of species). – Fowler, 1951: 565 (checklist of species). – Burgess, 1989: 278 (checklist of species). – Bockmann & Guazzelli, 2003:422 (checklist of species). – FerrarisJr., 2007: 196 (checklist of species). – Bockmann & Miquelarena, 2008: 45-46, table 3 (taxonomic treatment, Rhamdella revision, transfer to Pimelodella ). – Oyakawa & Menezes, 2011: 7 (checklist of species).

Pimelodella longipinnis . – Bockmann & Miquelarena, 2008: Table 3 (taxonomic treatment, transfer to Pimelodella ). – Slobodian et al., 2017: 96 (comparative material).

Diagnosis

Pimelodella longipinnis differs from all its congeners, except P. bockmanni Slobodian & Pastana, 2018 ; P. itapicuruensis ; P. leptosoma (Fowler, 1914) ; P. megalura Miranda Ribeiro,1918 ; P.metae Eigenmann, 1917 ; P.montana Allen, 1942 ; P. peruensis Fowler, 1915 , P. robinsoni , P.tapatapae Eigenmann, 1920 , P.wolfi (Fowler, 1941) and P. yuncensis Steindachner, 1902 , by having the supraoccipital process not reaching the anterior prenuchal plate (vs. supraoccipital process articulating with the anterior nuchal plate in all other Pimelodella species). From the remaining species, it differs from P. tapatapae by having the tip of the maxillary barbel reaching the region between verticals through pelvic-fin origin and anal-fin terminus (vs. reaching the caudal-fin origin). It differs from P. bockmanni , P. itapicuruensis , P. leptosoma , P. megalura , P.metae , and P.robinsoni by having dark coloration on lateral and dorsal regions of body (vs. body coloration paler, sometimes slightly darker anterodorsally). It differs from P.montana by the absence of a paired dorsolateral stripe extending from supraoccipital process to anterior one third of adipose-fin base (vs. a single dorsolateral stripe present). It is distinguished from P. peruensis and P. yuncensis by the dorsal fin presenting a hyaline stripe at the second fourth of dorsal-fin length, and maxillary barbel surpassing the vertical through pelvic-fin origin (vs. dorsal fin completely dark, without hyaline stripe; maxillary barbel very short, reaching the vertical up through half pectoral fin, but rarely surpassing the pelvic-fin origin).

When compared to Pimelodella species from the Mata Atlântica and Upper Paraná bioregions, Pimelodella longipinnis can be distinguished from P. avanhandavae , P. bahiana , P. boschmai , P. brasiliensis , P. eigenmanni , P. gracilis , P. harttii , P. ignobilis , P. kronei , P. lateristriga , P. meeki , P. pappenheimi , P. pectinifera , P. rudolphi , and P. transitoria by having the supraoccipital process not reaching the anterior prenuchal plate (vs. supraoccipital process articulating with the anterior nuchal plate in the mentioned Pimelodella species) and hypural 5 variably fused to hypurals 3+4 (vs. hypural 5 never fused to hypurals 3+4). Pimelodella longipinnis can also be distinguished from P.gracilis by the maxillary barbels reaching between verticals through pelvic-fin origin and anal-fin terminus (vs. maxillary barbels surpassing anal-fin terminus, usually reaching caudal-fin origin in P. gracilis ) and by 41-42 total vertebrae (vs. 46 total vertebrae). It differs from P. avanhandavae , P. bahiana , P. brasiliensis , P. eigenmanni , P. harttii , P. ignobilis , P. kronei , P. lateristriga , P. pappenheimi , P. rudolphi , and P. transitoria by the dorsal-fin spine being approximately half to two-thirds of first dorsal-fin ray total length (vs. dorsal-fin spine roughly threefourths of first dorsal-fin ray total length). It also differs from P. avanhandavae , P. gracilis , and P. itapicuruensis by the short adipose fin, three to four times in SL (vs. two and half to three times in SL in P. avanhandavae and P.itapicuruensis ; two to two and half times in SL in P.gracilis ). Pimelodella longipinnis further differs from all Mata Atlântica and Upper Paraná species by having an overall dark body coloration, with purplish hue in life, with dark brown midlateral stripe narrow, extending from posteri- or portion of orbit to caudal-fin origin.

Description

Morphometric data in Table 1. Body depressed, depth at dorsal-fin origin five to seven times in SL and compressed, body width at dorsal-fin origin seven to ten times in SL ( Fig. 1 ). Greatest body depth at dorsal-fin origin. Dorsal body profile convex from snout to origin of dorsal fin, slightly concave from that point to origin of adipose fin, convex along base of adipose fin, and concave along caudal peduncle. Ventral profile of body slightly convex from snout to branchiostegal membrane, then again convex in separate arc between branchiostegal membrane and pectoral-fin, convex between pectoral end pelvic fins, slightly convex from pelvic to anal fin, and concave from that point to caudal-fin origin.

Head moderately deep, head depth (at base of supraoccipital process) ½ to ⅔ of head length. Mouth subterminal. Eye elliptical, its longest diameter four to seven times in head. Bony interorbital distance slightly lesser than eye diameter.Barbels thin, slightly compressed,and elliptical in cross-section. Maxillary barbel when parallel to main body axis reaching to vertical through area between pelvic-fin origin and anal-fin terminus. Outer mental barbel when parallel to main body axis, reaching to verticals through area between origin and distal third of adpressed pectoral-fin. Inner mental barbel, when parallel to main body axis, reaching to verticals through area between posterior ventral limit of branchiostegal membrane and pectoral-fin origin. Supraoccipital process narrow, roughly rectangular, contacting the dorsal lamina of Weberian complex only at anterior tip. Branchiostegal rays 6 (49). Pseudotympanum large, oval, dorsal to posterior process of cleithrum and posteriorly reaching 6 th (2) or 7 th (2*) vertebra. Posterior process of cleithrum triangular, narrow, with straight dorsal margin. Anus and urogenital papilla adjacent. Urogenital papilla short, tubular and somewhat triangular. Anus roughly positioned at vertical through first third of adpressed pelvic fin; urogenital papilla near vertical through second third of adpressed pelvic fin.

Dorsal fin triangular, with concave distal margin. Longest dorsal-fin ray length four to six times in SL,its depressed tip reaching verticals through half or last fourth of adpressed pelvic-fin. Dorsal fin I,6 (49) plus anterior spinelet. Distance between terminus of dorsal-fin base and adipose-fin origin roughly equal to dorsal-fin base. First dorsal-fin pterygiophore inserted posterior to neural spine of vertebrae 5 (5); last dorsal-fin pterygiophore located posterior to neural (or pseudoneural) spine of vertebrae 10 (5). Unbranched dorsal-fin ray spinous for ca. 50-70% of its length, distal portion filamentous. No ornamentations on anterior or posterior margins of dorsal-fin spine.Pectoral-fin rays I,7 (5)or I,8* (45),pectoral fin triangular, margin concave. First pectoral-fin ray roughly straight with proximal part rigid, forming spine ( Fig. 2 ), short distal tip flexible and segmented, corresponding to the unossified actinotrichia bundle. Anterior margin of pectoral-fin spine with smooth serrae along its distal third, and minute denticulations along its proximal half to two-thirds (denticulations progressively more spaced distally); posterior margin with 8-10 straight to retrorse serrae along its basal two-thirds. Distalmost posterior serrae larger and more curved than 2-3 basal ones. One or two additional unossified distal serrae present (not included in counts). Pelvic-fin rays i,5 (50), expanded pelvic fin triangular with straight distal border. Pelvic-fin origin at vertical through terminus of dorsal-fin base.Tip of adpressed pelvic fin at vertical through origin of adipose fin. First unbranched ray not spinous, distinctly shorter than second and third ones; third ray longest, slightly longer than second one; remaining rays progressively shorter. Anal-fin ray formula variable, ii,8 (1); iii,8 (3); iv,8 (2); iii,9 (11); iv,9 (12*); iii,10 (4); iv,10 (1); v,10 (2) or iii,11 (2). One to three additional anterior accessory analfin rays present, embedded in thick integument, and not included in anal-fin ray count. Anal-fin distal margin convex when expanded. Anal fin origin at vertical through first third of adipose-fin base; adpressed anal-fin terminus between verticals through adipose-fin terminus or a point slightly anterior to that.First anal-fin pterygiophore posterior to haemal spine of vertebrae 20 (1), 21 (4) or 22* (1). Last anal-fin pterygiophore posterior to haemal spine of vertebrae 27 (1), 28 (3), 29 (1) or 30* (1). Adipose fin short,three to six times in SL,forming ascending curve in lateral profile, with deepest point approximately at midlength. Adipose fin emerging gradually, its posterior limit forming round free lobe. Adipose-fin origin at vertical through vertebral centra 20* (2), 22 (2) or 23 (1); fin terminus at vertical through vertebral centra 35 (3), 36 (1) or 37* (1). Caudal fin deeply forked, lobes equal in length or with dorsal one slightly longer. Caudal-fin dorsal lobe with 11 (1)-17 (1) (holotype 13) procurrent fin rays, followed by 1 (50) unbranched and 7 (50) branched principal fin rays. Ventral lobe with 11 (1)-19 (1) (holotype 14) procurrent fin rays, followed by 1 (50) unbranched and 8* (48) or 9 (2) branched principal fin rays.

Hypural 5 free (3) or fused* (2) to complex plate formed by co-ossified hypurals 3 and 4. Median caudal-fin rays not articulating directly with hypural plate. Seven (6) rays articulating with dorsal caudal-fin plate (5 on hypurals 3+4 and 2 on hypural 5) and 7 (2) or 8* (4) rays articulating with ventral caudal-fin plate (5 or 6 on hypurals 1+2 and 2 on parhypural).Total vertebrae 41 (3) or 42* (4). Ribs 8* (1)-10 (1), usually 9 (5).

Epiphyseal branch of cephalic laterosensory canal(S6) emerging onto skin as two narrowly distanced pores* (46) or, less frequently, as a unique pore (S6+S6) (7).

Figures

Figure 1. Left lateral (A) and dorsal (B) views of Pimelodella longipinnis (Borodin, 1927), AMNH 8642, holotype of Rhamdella longipinnis, 84.6 mm SL. Photo pro- vided by AMNH staff.

Figure 2. Ventral view of left pectoral-fin spine of Pimelodella longipinnis, AMNH 8642, holotype of Rhamdella longipinnis, total length of spine 11.5 mm.

Figure 3. Left lateral view of an ethanol-preserved,recently collected specimen of P.longipinnis, MZUSP 116324,57.6 mm SL.

Figure 4. Live specimens of P.longipinnis, showing the coloration in life (preserved in MZUSP 116324).